1. Field of the Invention
The present invention relates to optical recording apparatuses such as optical disk recording apparatuses. More specifically, the present invention relates to an optical recording apparatus provided with a reference value that is useful in testing recording quality.
2. Description of the Related Art
In recording of data on optical information recording media such as CD-R and DVD-R (hereinafter referred to as a medium), matching between a medium on which data is to be recorded and a recording apparatus (hereinafter referred to as a drive) used for recording differs among combinations of a medium and recording apparatus. This is due to factors relating to the medium such as variation in optimal recording condition due to difference in the type of recording material of the medium or due to variation that occurs in film formation during manufacturing, and due to factors relating to the drive such as variation in optimal recording condition due to variation in assembly during manufacturing or due to difference in the type of pickup or semiconductor laser included in the drive. Practically, a recording condition that is suitable for each combination of a medium and a drive is determined by a combination of these factors.
Thus, conventionally, ID information that allows a drive to identify the type of a medium is stored in the medium, and recording conditions prepared in advance for individual media types are stored in the drive. When information is actually recorded, ID information of a medium loaded onto the drive is read from the medium, and a recording condition associated with the ID information is used.
Although the conventional method allows to select a recording condition that is suitable to a certain degree for a medium of a known type that has been examined in advance, in some cases, prepared recording conditions are not suitable for a medium of an unknown type that has not been examined. Furthermore, prepared recording conditions are sometimes not suitable even for a medium of a known type, depending on, for example, recording speed, disturbance, or aging.
Japanese Unexamined Patent Application Publication No. 2001-126254 describes a method for dealing with media of unknown types. According to the method described in the document, in order to allow a drive to obtain by itself an optimal recording condition on a medium-by-medium basis (refer to paragraph 0009), an asymmetry value β and a pit length obtained by carrying out playback with a reference disk are stored in an EEPROM of the drive (refer to paragraph 0028). A β value obtained by carrying out test recording with a medium to be used for recording is compared with the β value stored in the EEPROM, and recording strategy is corrected so that desired β value and pit length will be achieved (refer to paragraphs 0029 to 0031).
According to the method, recording strategy can be optimized on a medium-by-medium basis. Accordingly, the capability of dealing with media of unknown types is improved. Furthermore, since desired β value and pit length are set on a drive-by-drive basis, variation caused by factors relating to drives is absorbed (refer to paragraph 0036).
According to the method, however, since playback is carried out with a reference disk having pits conforming to a predefined standard and a result obtained by the playback is used as a reference value for the drive, various factors that affect recording are not considered, so that the method is not sufficient to provide a standard recording environment.
Furthermore, optimal value of β differs among individual media due to the nature of β value. More specifically, β=0 is not an optimal value for all media. For example, β=5% is an optimal value for a medium A, while β=10% is an optimal value for a medium B. Thus, a β value obtained simply by carrying out playback with a single reference disk does not serve as a criterion for testing quality of other media, so that it does not suffice as a criterion for testing recording quality.
Furthermore, the β value used as a criterion is not necessarily an optimal value. It is possible that the drive allows a more suitable recording condition but the result of the playback with the reference disk is used as a criterion. Therefore, a room for improvement exits as to the capability of dealing with media of unknown types.
Furthermore, according to the method, since the recording strategy is corrected so that β value and pit length will be closer to desired values, it is difficult to deal with a combination of a drive and a medium for which it is not possible to adjust to desired values.
Furthermore, since the β value and pit length that are used as reference values in the method are values desired for recording by the particular drive, it is difficult to evaluate matching between drives and media based on the magnitudes of these values. Therefore, the β value and pit length are not sufficient as criteria for evaluating matching between drives and media.